The subject matter disclosed herein relates to the magnetization of permanent magnets, and more specifically, to the magnetization of magnets disposed within cylindrical structures using one or more superconducting materials.
Many electrical machines include one or more electric motors. Such electric motors typically include a rotor having permanent magnets disposed within the bulk of the rotor. During rotation, the rotor, having the permanent magnets, produces a rotating magnetic field that interacts with a stator. This electromagnetic interaction results in the conversion of electromagnetic energy into mechanical motion that drives the machine.
Two approaches are typically used for the assembly of rotors having permanent magnets. In one approach, shaped materials are magnetized to generate the permanent magnets before they are disposed within the bulk of the rotor. This approach may present several drawbacks. For instance, fully magnetized permanent magnet pieces can be subject to electromagnetic interaction with any surrounding objects, such as other adjacent or proximate magnets, which in turn adds to the complexity of their handling procedures and insertion into the rotor. In a second approach, the shaped materials are first disposed within the rotor and a magnetizer is used to magnetize the permanent magnets. Such an approach is typically referred to as an in-situ magnetization process.
The second approach can also present several drawbacks. To name a few, the energy and fabrication costs for conventional resistive magnetizers capable of generating a sufficient magnetic field flux for the magnetization process can be prohibitive. For example, some in-situ magnetizers are able to produce small magnetic fields sufficient only to magnetize small permanent magnets made of certain materials or grades (e.g., alnico and ferrite) that have low intrinsic coercivity (i.e., materials that can be easily demagnetized). However, many emerging applications for permanent magnet electric machines, such as wind turbine applications, or traction (e.g., magnetic bearing and braking) applications, would benefit from the use of high-coercivity rare-earth permanent magnet materials, which can often require strong magnetic fields. Moreover, as the permanent magnets increase in size, their magnetization becomes increasingly difficult due to inadequate field penetration produced by typical magnetizers. It should therefore be appreciated that due to physical constraints in addition to economic considerations, the in-situ magnetization of such materials is typically very difficult to deliver with conventional restive systems. Accordingly, it is now recognized that a need exists for a magnetizer capable of magnetizing rare-earth, high-coercivity materials in an efficient manner.